<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>文本样式</title>
    <style>
        div {
            color:red;
            font-size:50px;
            text-align:center;
            text-decoration:none;
        }
        .tip{
            color:red;
            font-size:12px;
            font-family:"Arial Black";
            font-style:italic;
        }
    </style>
</head>
<body>
<div>
    zbdx
</div>
用户名<input type="text" placeholder="请输入用户名">
<span class="tip">用户名不合法！
</span>
</body>
</html>